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Difficulty: MediumNetworking Ports and Protocols

A network administrator is setting up infrastructure services for a new branch office subnet. Client workstations on this subnet must automatically receive dynamic IP address configurations upon booting and must also be able to translate human-readable domain names into IP addresses. Which of the following port numbers must be opened on internal network firewalls to support these required client capabilities? (Select TWO).

  1. UDP port 67Answer
  2. UDP and TCP port 53Answer
  3. C
    TCP port 80
  4. D
    UDP port 69

Answer

UDP port 67 (DHCP server destination) and UDP/TCP port 53 (DNS service queries).
DHCP enables automatic network configuration by communicating over UDP port 67 (server port) and UDP port 68 (client port). DNS translates domain names into IP addresses and operates on port 53 over UDP for standard name resolution queries and TCP for larger data exchanges. Both ports are required to meet the scenario's stated requirements.

Step-by-Step Solution

1
Identify the required network service for automatic IP address configuration.
Dynamic Host Configuration Protocol (DHCP) operates on UDP ports 67 (server listener) and 68 (client listener).
Client workstations require DHCP to receive IP addresses, subnet masks, default gateways, and DNS server details dynamically.
2
Identify the required network service for hostname-to-IP translation.
Domain Name System (DNS) operates on port 53 using both UDP (for standard client queries) and TCP (for zone transfers and large responses).
Client workstations require DNS resolution to convert domain names into IP addresses.
3
Select the option choices corresponding to DHCP and DNS standard listening ports.
UDP port 67 and UDP/TCP port 53 are selected.
Opening UDP 67 permits client DHCP discover/request packets to reach the DHCP server, while port 53 permits client DNS name queries.

Key Concept

Core Network Service Port Assignments (DHCP on UDP 67/68 and DNS on UDP/TCP 53)
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Topics

Networking Ports and Protocols

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